1. Field of the Invention
This invention relates to a card medium having patterns such as embossed characters, numerics and symbols or the like, and particularly to a structure for preventing forgery of patterns embossed on the card medium and a method of manufacturing the structure.
2. Description of the Related Art
There has recently been an increasing tendency to use cards for payment and withdrawal of money to and from a bank, for the purchase of goods and for identification of an employee. Various types of such cards are known. As examples, a card capable of magnetically recording information therein and a card equipped with an integrated circuit having a memory and capable of allowing the memory to store information therein are known. Such information is generally used as information to be kept secret from those other than the card owners in most cases. To the contrary, information that may be known by those other than the card owners, is also included therein. For instance, the names of the card owners themselves and identification numbers such as account numbers individually applied to card owners by an agency that has issued cards thereto, are included in the information. Such information may preferably be set such that when a card owner has lost or dropped his or her card, a card finder can immediately confirm to which person the card belongs. Therefore, embossed patterns are provided on a card so that such information can be confirmed from the external appearance of the card. The patterns are comprised of a plurality of characters, numerics and symbols or combinations of these because of the names or identification numbers referred to above.
However, there may be cases where the patterns embossed on the card are imitated or forged or put to a bad use. There is therefore a demand for improving a technique for preventing card forgery. The embossed patterns are easy to be forged. Forgery is realized by, for example, pressing a card having embossed patterns so as to flatten the front and back of the card and thereafter embossing desired patterns therein.
Further, the embossed patterns can be simply provided on the card using molds or the like by a card issue agency. Thus, since the embossed patterns are easily formed, the application of complex processes for prevention of forgery of the embossed patterns is at variance with the reality.